Development of Multifunctional ZnS Ceramic Materials with Enhanced Optical Transparency and Antibacterial Activity

Zinc sulfide (ZnS) ceramic materials were successfully synthesized using a sol–gel method followed by thermal annealing at 500 °C and 700 °C to investigate the influence of annealing temperature on their structural, morphological, optical, vibrational, and antibacterial properties. X-ray diffraction (XRD) analysis confirmed the formation of a highly crystalline single-phase cubic zinc blende ZnS structure without detectable secondary phases. Thermal annealing significantly enhanced crystallinity, increased the average crystallite size from approximately 18.6 nm to 36.5 nm, and reduced lattice microstrain and dislocation density, indicating improved structural ordering. FESEM observations revealed uniformly distributed nearly spherical nanoparticles with average particle sizes increasing from approximately 42 nm to 81 nm after annealing, while EDX and elemental mapping verified the homogeneous distribution of Zn and S with high compositional purity. Optical characterization demonstrated excellent transparency exceeding 85% in the visible region together with a slight reduction in the direct optical band gap from 3.80 eV to 3.72 eV, attributed to crystal growth and reduced structural defects. .